1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, a process cartridge that is detachably mountable to the main body of the apparatus, and an optical guide for detecting the developer amount of the developer-containing portion of the apparatus.
Now, the electrophotographic image forming apparatus is an apparatus for forming an image on a recording medium by the use of an electrophotographic image forming process. As examples of the apparatus, an electrophotographic copying machine, an electrophotographic printer (e.g. a laser beam printer, an LED printer, and the like), a facsimile machine, a word processor and the like can be cited.
Moreover, a process cartridge may be a cartridge into which charging means, developing means or cleaning means, and an electrophotographic photosensitive drum are integrally incorporated, and which is detachably mountable to the main body of the electrophotographic image forming apparatus. Alternatively, the process cartridge may be a cartridge into which the electrophotographic photosensitive drum and at least one of the charging means, the developing means and the cleaning means are integrally incorporated, and which is detachably mountable to the main body of the electrophotographic image forming apparatus. Further alternatively, the process cartridge may be a cartridge into which the electrophotographic photosensitive drum and at least the developing means are integrally incorporated, and which is detachably mountable to the main body of the electrophotographic image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as a printer using an electrophotographic process records an image as follows. That is, first, a photosensitive drum being an image-bearing member is uniformly charged. The photosensitive drum is selectively exposed to light, thereby forming a latent image. The latent image is visualized with toner, which is developer. The visualized toner image is transferred to a recording medium. Moreover, by the application of heat or pressure on the transferred toner image, the toner image is fixed on the recording medium. Thus, the image is recorded.
Such an apparatus needs the supply of toner and maintenance of various kinds of process means. However, a cartridge equipped with a photosensitive drum, charging means, developing means, cleaning means and the like integrally therein is put to practical use as a measure for simplifying the toner supplying work and the maintenance.
A developing device of such a process cartridge is equipped with a developer-remaining-amount detecting device for detecting a remaining amount of the stored developer. The developer-remaining-amount detecting device is realized in conformity with various modes. A mode cheaper in cost and simpler in structure is one adopting light-transmission-type remaining-amount detection. The light-transmission-type remaining-amount detection is a mode such that detection light passes through a container containing developer therein for the detection of the remaining amount of the developer contained in the container on the basis of the passing time of the detection light.
A description will be given to the detailed structure of the light-transmission-type remaining-amount detection device in the following. As shown in FIG. 12, detection light emitted by a light-emitting member such as a light-emitting device passes through a first guide portion 31a made of a light-transmissive member, and then the detection light enters the inside of a developer container 25 from a first window member 26a that is formed on the wall surface of the developer container 25 and has a light-transmissive property. Moreover, the detection light that has entered in the developer container 25 passes through the developer container 25 to the outside of the developer container 25 through a second window member 26b that is formed on the wall surface of the developer container 25 and has a light-transmissive property. The detection light that has passed through to the outside of the developer container 25 reaches a light-receiving member such as a light-receiving element through a second guide portion 31b made of a light-transmissive member. The developer-remaining amount in the developer container 25 is detected on the basis of the period of time when the light-receiving member received the detection light. Incidentally, the technology shown in FIG. 12 is not a prior art. The configuration shown in FIG. 12 is earlier technology that was considered in the process of the development of the present invention.
In the above earlier technology, in each of the first and the second guide portions 31a and 31b, both being a light-transmissive member, the light-emitting member or the light-receiving member is disposed at one end thereof and an incidence plane or an exit plane is disposed at the other end in the vicinity of the first or the second window member 26a or 26b. Consequently, when the window member 26a or 26b or the incidence or exit plane opposed to the window member 26a or 26b becomes dirty, a light-transmission loss increases. Moreover, because the media between the incidence plane or the exit plane of the optical guide portion 31a or 31b and the window member 26a or 26b are different from each other, a diffused light phenomenon and reflection occur at the boundaries between the different media. This phenomenon also causes the loss of light.
Moreover, because the optical guide portions 31a and 31b are made from acrylic resin and, on the other hand, the container of the process cartridge is made from polystyrene, it is impossible to perform hot welding or ultrasonic welding of the optical guide portions 31a and 31b to the container. Accordingly, the optical guide portions 31a and 31b are fixed to the container with fixing means mechanically. Consequently, many parts are needed for the detection of the amount of remaining developer as the optical guide portions 31a and 31b, the window members 26a and 26b, and the fixing means. Moreover, because each part is small in size, the fixing of them requires a lot of care.
Besides, a space is needed to dispose the fixing means.
An object of the invention is to provide an optical guide having less loss of light , a process cartridge using the optical guide, and an electrophotographic image forming apparatus capable of mounting the process cartridge detachably.
Another object of the invention is to provide an optical guide easy to fit, a process cartridge using the optical guide, and an electrophotographic image forming apparatus capable of mounting the process cartridge detachably.
A further object of the invention is to provide an optical guide capable of decreasing the number of its parts, a process cartridge using the optical guide, and an electrophotographic image forming apparatus capable of mounting the process cartridge detachably.
A still further object of the invention is to provide an optical guide that needs less space for fitting, a process cartridge using the optical guide, and an electrophotographic image forming apparatus capable of mounting the process cartridge detachably.
A still further object of the invention is to provide an optical guide for detecting the remaining amount of developer, which optical guide has less light-transmission loss and needs a smaller space for fitting and smaller number of parts and is easy to fit, a process cartridge fitted with the optical guide, and an electrophotographic image forming apparatus capable of mounting the process cartridge detachably.
A still further object of the invention is to provide an optical guide having the following features, a process cartridge using the optical guide, and an electrophotographic image forming apparatus capable of mounting the process cartridge detachably. The optical guide is formed into one united body with a light-transmissive material and comprises a blocking portion for blocking an opening formed in a developer containing portion when the optical guide is fitted to the developer containing portion, an optical guide portion for guiding light, the optical guide portion being disposed on the outside of the developer containing portion with respect to the blocking portion when the optical guide is fitted to the developer containing portion, an outside inclining surface portion disposed at an end portion of the optical guide portion on the blocking portion side in the lengthwise direction of the optical guide portion, the outside inclining surface portion inclining to the side on which the optical guide portion is provided, an inside inclining surface portion disposed on a side positioned on the inside of the developer containing portion with respect to the blocking portion when the optical guide is fitted to the developer containing portion, the inside inclining surface portion inclining in a direction intersecting the lengthwise direction of the optical guide portion.